Percussion generating circuit for electric organs



United States Patent 3,484,531 PERCUSSION GENERATING CIRCUIT FOR ELECTRIC ORGANS Glenn A. Schmidt, 6325 Fair Place, Los Angeles, Calif. 90043 Filed Mar. 10, 1966, Ser. No. 533,368 Int. Cl. Gh 1/02, 3/00 US. Cl. 84-1.26 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates generally to electric organs and in particular to a novel semiconductor circuit which may be added to an existing organ by which an improved percussion characteristic may be added to the tonal capabilities of the organ economically, and which is operable over a wider range of manuals and octaves in the organ than is possible with presently available percussion generating systems.

In the general operation of percussion attack functions in existing electric organs, the means by which such attack functions are generated do not permit the percussion characteristic to be operable for more than single harmonics,

as these tones in the prior art means are generated for particular tones and do not permit these tones to be heard along with the harmonics thereof also sounding in the percussive mode.

A percussive tone may be described as that generally associated with hammer-struck strings, as in the piano, or in plucked string instruments. In the piano, the tone amplitude rises rapidly, almost abruptly, upon the hitting of the string by the hammer when the piano key is struck. The tone then decays rapidly in a fashion known to those familiar with wave phenomena as a damped wave. Similar sharp rise sound patterns followed by an exponential decay characteristics are experienced with snare drum and tympani. The steepness of the slope of the decay portion of the characteristic of a percussion tone is different for different instruments. A Hawaiian guitar tone will have a relatively long decay compared to a pizzicato violin.

Certain electric organs have provided such organ tones as are similar to a piano tone in attack and decay pattern, but when applied permit only a single tone to respond to the percussive action, but do not permit more than one of the harmonics of that tone to respond with the percussive reaction also.

This invention contemplates electronic semiconductor (solid state) circuit means which may be installed in a particular circuit area of an existing organ such as, for example, the Hammond organ whereby an improved and more effective percussion characteristic can be imparted to any tone generated in the organ and which will also create the percussive effect simultaneously in four or more of the harmonics or subharmonics of the tone being played.

The new circuit means is installed in the organ by inserting it in series with one cross-bar line of a draw-bar circuit so that when the draw-bar is extracted to the cross bar position in which the circuit of this invention is installed, all tones generated will operate with the percussive ice attack and decay characteristic for which the new circuit may be adjusted. Each key which is fingered produces a percussive tone, which also is applied to the appropriate harmonics of the tone that make the selected tone sound like a particular instrument or voice. The decay slope characteristic, or duration of the sound envelope, and the attack characteristic of the tone generated with the use of the invention, may be adjusted so that a variety of different decay and attack combinations are possible. These may be created for effects such as the sharp pulses of the snare drum or tympani through those of tones like the plucked string or hammer-struck string.

By the installation of this invention in an organ as described above in the common output line of the selected draw-bar circuit any tone, sequence of tones, or combination of tones normally released to the output through that draw-bar line will be produced with the characteristic percussive features of attack and decay as set up with the adjustable means incorporated in the invention.

The new circuit may be described as a feed through amplifier isolated by buffer means from a wave shaping and variable control impedance means for the amplifier so that the resulting output to the organ amplifiers is the generated tone with an amplitude characteristic shaped by the control signals developed in the device of the invention in response to the tone itself.

The new percussion generating circuit of the invention can be installed in an existing organ for a cost no more than one fifth of the cost of adding similar prior art devices to organs. The prior art devices are only capable of limited operation.

The new device of this invention may be installed in any existing organ of the Hammond type previously mentioned, including the compact spinet type. It can be adjusted by the organist to sound like existing percussion systems and also to create new and expanded effects not possible with the existing systems. It can provide for onolf, loud-soft, or long or short decay operation. The new device can also provide second and third harmonic operation and others which are not possible with prior art devices.

The new device can do many other things not possible with the prior art devices. For example:

All draw-bar units can be percussed individually, collectively, or in any selected combination;

All manuals can be percussed individually, collectively, or in any combination, so long as the manual or pedal outlet is through the eighth cross-bar of the draw bar;

Percussion may be applied to any preset combination by setting the voices on eighth cross-bar outputs.

Accordingly, the invention has for its principal purpose the provision of novel circuit means insertable in a common audio output line of a tone generating system of an electric organ whereby percussion effects may be created in any tone generated on any manual, along with appropriate harmonics of the tones, individually, collectively, or in any selected combination of tones or manuals.

A representative embodiment of the invention is described in the specification which follows. The embodiment should not be construed as limiting the invention thereto, since those skilled in the arts pertaining hereto will be able to conceive other embodiments in view of the teachings herein from the specification and claims taken together with the drawings in which:

FIGURE 1 is a schematic circuit diagram of the invention showing a representative form thereof;

FIGURE 2 is a fragmentary circuit detail showing the connection of the circuit of the device into the cross bar circuits of the organ in which the invention is installed; and

FIGURE 3 is a typical percussion tone waveform showing the elements of such a waveform for explanatory purposes.

The circuit schematic diagram of FIGURE 1 is an exemplary circuit for implementing the invention. In FIG- URE 1 are shown a series of transistors 10, 20, 30, 48, 5t), 60 and 70. Transistor is an NPN device employed in the circuit as an isolating input and pre-amplifying amplifier which provides an impedance matching transformation and load splitting action between the tone generating source device and the circuit of the invention. Transistor is an NPN device and is employed as a buffer amplifier between the input amplifier and the control circuit to be described below. Transistor 30 is also an NPN device and is used as the first quench signal amplifier. Transistor 40 is a NPN device and is the second quench signal amplifier and wave shaper. Transistor 50 is a PNP device employed as a D-C amplifier.

The transistor 60 is considered the heart of the invention and is responsible for its novel performance and character. Transistor 60 is an NPN device and is a novel variable control impedance.

Transistor 70 is an output emitter follower amplifier to provide both output isolation and impedance transformation for the device of the invention.

Transistor 10 has the emitter 11 thereof connected to a negative D-C power line 19. The collector 12 of transistor 10 is connected through a load resistor 17 to a positive D-C power line 18. Lines 18 and 19 are normally connected to a battery or a well regulated D-C power source derived from A-C lines by well-known rectifier circuit techniques. A base bias and feedback resistor 16 is connected between collector 12 and base 13 of transistor 10.

An input coupling capacitor 14 is connected between base 13 and an input circuit terminal 15. To the collector 1-2 are also connected the base 23 of transistor 20 and a coupling resistor 24 which is in series with a coupling capacitor 25 connected to the base 33 of transistor 30. Resistor 24 acts as a signal current limiting resistor and isolation in coupling signals from transistor 10 to transistor 30.

The collector of transistor 20 is connected directly to positive D-C power line 18. The emitter 21 of transistor 20 is connected through a series resistance pair 26, 27 to negative DC power line 19. The junction 29 of resistors 2 6 and 27 is the emitter follower output of transistor 20 to be further described below.

The emitter 31 of transistor is directly connected to negative D-C line 19. The collector 32 of transistor 30 is connected through a load resistor 35 to positive D-C supply line 18. A base bias and feedback resistor 34 is connected between base 33 and collector 32. A coupling capacitor 36 is connected between collector 32 and base 43 of transistor 40.

The emitter 42 of transistor 40 is connected directly to positive D-C line 18. The collector 41 of transistor 40 is connected through a load resistor 45 to negative D-C line 19. A resistor 39 is connected between base 43 and positive D-C line 18. An output coupling capacitor 46 is connected from the collector 41 to the junction 49, 59 of a pair of diodes (D1 and D2) connected in a half-wave voltage-doubling circuit relation between positive D-C line 18 and the base 53 of transistor 50. A load resistor 57 is connected from the junction 49, 59 of diodes D1 and D2 to negative D-C line 19. A charge storage capacitor 54 is connected between base 53 of transistor and the positive D-C line 18. A base bias resistor 58 is connected between base 53 and negative D-C line 19. The emitter 52 of transistor 50 is connected directly to positive D-C line 18. The collector 51 of transistor 50 is connected through a load resistance 55, 56 to negative D-C line 19. Resistor 56 is variable. A filter capacitor is connected between collector 51 and negative D-C line 19. A resistor 67 connects from collector 52 to base 63 of transistor 60.

Collector 61 of transistor 60 is connected through a load resistor 69 to positive D-C line 19. The emitter 62 of transistor 60 is connected through a potentiometer 68 to negative line 19. The arm 64 of potentiometer 68 is connected through capacitor 66 to base 23 of transistor '70. Collector 72 of transistor is connected through a load resistor 75 to positive D-C line 18. The emitter 71 is connected through a load resistor 76 to negative D-C line 19. A bias and feedback resistor 74 is connected from collector 72 to base 73. A filter capacitor 79 is connected from collector 72 to positive D-C line 19. An output coupling capacitor is connected between emitter 71 and an output terminal 78.

A coupling capacitor 28 is connected from junction 29 to collector 61 of transistor 60.

In FIGURE 2 the circuit connections for the amplifier shown in FIGURE 1 and above described to be inserted in an organ are presented. Since organ circuit people are familiar with the major parts of an organ, only those directly involved in the connection of this invention are shown.

8 upper crossbars is identified in FIGURE 2 at 101. This is sometimes described in the literature as a bus bar, and in the Hammond type of organ is found in the harmonic draw bar circuit. There are typically nine harmonic drawbars associated with a lower manual, and nine associated with the upper manual. By sliding these drawbars the organist can mix the fundamental and harmonies in various proportions. The degree of strength of the harmonic inserted is determined by how far out the bar is drawn is drawn. The draw bars contact one of nine cross bars or bus bars. These are numbered as zero, and one through eight. When a draw bar is pulled to a particular cross bar contact, the harmonic of a tone it represents is delivered to an appropriate tap on a mixer transformer. The 8 cross bar for any manual is connected to the mixer or to the device of this invention when the draw bar is fully extended. Thus, as will be clearer from the discussion below, to operate the system of this invention it is merely necessary to pull the draw bar fully out to make connection with the 8 cross bar.

Referring back to FIGURE 2, the 8 upper cross bar 101 lead 110, usually color-coded gray, is broken and the arm connections 108, 109 of a double pole double throw switch 103- connected to the open ends 108, 109. Arms 108, 109 are mechanically coupled together as indicated at 124. One set of contact poles 105, 107 are connected together so that when arms 108, 109 are connected thereto the gray lead 110' is completed to draw bar 101. This is the off condition of the system.

The other poles 111, 112 of switch 103 are connected to the input 15 and output 78 of the circuit of FIGURE 1. Similarly switch 104 is connected to lead 118 of lower cross bar 102 with arms 115 and 117 in series with gray lead 118 and off terminals 113 and 114 connected together. Note that the same mechanical coupling 124 connects switch 104 as does 103. Thereby switches 103 and 104 operate together in tandem for the off condition to connect the gray leads 110, 118 to their respective cross bars, 101, 102 independently of one another and for the on condition to insert the amplifier and control system of FIGURE 1 to the outputs represented by both cross bars 101 and 102. Since both leads 110 and 118 are connected to the organ tone signal mixer it is of no consequence that leads 122 and 123 connect both gray leads 110 and 118 through the circuit of FIG- URE 1 when the switches 103 and 104 are in the on condition.

The operation of the system may now be bettter understood with reference both to FIGURES 1 and 2 and also with respect to FIGURE 3 in which a representative signal 132 emanating from the system is shown. The signal consists of the tone proper 132 which has been amplitude modified by the circuit of this invention,

as shown in FIGURES 1 and 2. The operating envelope 131 is created by the circuit of FIGURE 1.

Amplifier in FIGURE 1 receives the tone signal generated when an organ manual key is depressed and the draw bar connects the mixer via gray leads 110 or 118 to cross bar #8. This signal is applied through capacitor 14 to base 13. From collector 12 the signal then is applied to base 23 directly and through coupling network 24, 25 to base 33. Transistor 60 is normally conductive and is so conductive at this time. Via capacitor 28 from emitter 21 the signal passes through transistor 60 across resistor 68 and in proportion to the setting of arm 64 will be applied through capactior 66 to transistor base '73 to appear on the emitter '71 and across capacitor 77 to output terminal 78, with the full amplitude of the signal.

Meanwhile, through transistor amplifier 39 and shaper 40 the signal is applied via capacitor 46 to diodes D1, D2 where a voltage doubling rectifying action takes place to charge capacitor 54 to a positive potential on base 53 with respect to line 18 which overcomes the bias on base 53 normally applied through resistor 58 and causing transistor 50 to become non-conductive. Capacitor 65 which had been charged with the difference of potential due to the drop across resistors 55 and 56 now discharges through resistors 55 and 56 at a rate determined by the value of capacitor 65 multiplied by the resistance of the resistors 55 and 56 as set by the adjustment of variable resistor 56. Ultimately the charge on capacitor 65 is dissipated and the base 63 of control impedance transistor 60 has zero potential thereon to render it non-conducting and the signal up then appearing at output 7 8 is terminated. The pattern of the operation of the above described sequence is that illustrated in FIGURE 3.

At 130 of FIGURE 3 the condition of no tone is shown. The switches 103, 104 are placed in on condition and the power applied to lines 1849 whereupon, in addition to amplifiers 10, 20, 30 and 40 becoming operative, so does amplifier 50, 60 and 70. Capacitor 65 charges as soon as amplifier 50' is operative. As soon as a tone is struck, it is applied from cross bar #8 at 101 or 1112 to input of the circuit of FIGURES l and 2, and then it appears at output 7 8 at the full amplitude 135 while it also appears at diodes D1 and D2 to produce the control signal as above described. When D-C amplifier 5t) ceases conduction the discharge of capacitor 65 through resistors 55 and 56 begins and follows the damped wave contour 131 to cut off control impedance 60 and end the transmission of signal along gray wires 110 and 118 to the organ mixer. This occurs for every tone generator which is connected through the eighth cross bars.

What is claimed is:

1. A percussion signal generator for insertion in a selected cross bar lead of the draw bar assemblies on an electric organ manual, said generator comprising in combination:

double pole single throw switch having closed and open contacts connected in the cross bar lead so as to complete the circuit of said lead through said closed contacts in an off position thereof and to provide an open circuit in said lead in an on position thereof, through said open contacts;

a signal dividing amplifier means having an input connected to one terminal of the selected cross bar lead in the on position of said switch to receive a tone signal therefrom, and having a first and a sec- 0nd output means, said tone signal being applied to said first and second output means;

a control impedance means having an input connected to said first output means to receive a tone signal therefrom directly and to normally conduct said tone signal to an output circuit connected to the other terminal of said cross bar lead in the on position of said switch; said control impedance being adapted to be responsive to a control signal to become nonconductive;

a direct current control signal generating means connected to said second output means of said signal dividing amplifier means and adapted to be responsive to the portion of said tone signal applied thereto to develop therefrom a D-C control signal; and

settable resistance capacitance discharge timing means coupled to said direct current control signal generating means and to said control impedance means and being adapted to be responsive to said DC control signal to reduce the conductivity of said control impedance means at a decay rate determined by the setting of said resistance capacitance discharge timing means,

whereby said tone signal is conducted between said input and said output circuit initially at full output level and thereafter at a rate of decay determined by said resistance capacitance discharge timing means to produce a percussion tone having an initial sharp rise to full amplitude followed by a decay of predetermined rate and slope as selected by said settable timing means.

2. The percussion signal generator means defined in claim 1 wherein said control impedance means is a transistor amplifier having a base, a collector and an emitter wherein normal feedthrough coupling is present between collector and emitter and said coupling being controlled by the bias on the base thereof, and wherein both said collector and said emitter are returned to a common circuit polarity.

3. The percussion signal generator means defined in claim .1 wherein said direct current control signal generating means is a voltage doubling rectifier responsive to the tone signal to derive said D-C control signal.

4. The percussion signal generator means defined in claim 1 wherein said signal dividing amplifier means includes a first amplifying transistor having a base, a collector, and an emitter, said base being connected to said input, said collector being connected to both said first output means and to said second output means, said first output means being an emitter follower connecting said first output means to said control impedance means and said second output means being a two-stage amplifier coupling said first amplifying transistor to said direct current control signal generating means.

References Cited UNITED STATES PATENTS 3,160,694 12/1964 Melnema 84--1.13 X 3,383,453 5/1968 Sharp 84-1.13 X

HERMAN K. SAALBACH, Primary Examiner F. PRINCE BUTLER, Assistant Examiner US. Cl. X.R. 84-l.13 

